1. Technical Field
The present invention relates to a method for the production of a tubular knitted article with a closed end, for example such as a sock, a stocking, a tubular part for the production of tights, or the like.
More specifically, the invention relates to a method of the abovementioned type in which the tubular article is produced on a circular knitting machine with a circular bed or needle cylinder, and in which the end is closed on the same machine as that on which the article was knitted, subsequent to the knitting of this article.
The invention also relates to a device for closing the end of the tubular knitted article directly on the machine by which the article was knitted.
2. State of the Art
In the production of tubular knitted articles, such as stockings, socks, tubular parts for tights and the like, the tubular articles are normally knitted beginning at an initial end and finishing at a final end on a needle cylinder. The tubular article produced in this way has two open ends, one of which must then be closed by sewing or some other suitable method. The article with its open ends is normally released from the needle bed or cylinder of the knitting machine and transferred to a sewing machine where, sometimes with partial manual intervention, the article must be correctly positioned and the end to be closed must then be fed into a sewing machine. If, as often happens, the article is not symmetrical but has, for example, a heel, it must first be correctly oriented before the seam is put in, so that the seam is correctly oriented relative to the heel. This involves a large labor input and therefore high costs.
This process is very time-consuming and costly owing in part to the need to provide machinery for positioning and sewing articles that have been produced on a separate knitting machine.
In order to eliminate these problems, a method and a device have been suggested (see EP-A-0,592,376) for closing an end, that is the toe, of the tubular article directly on the circular needle bed or cylinder of the knitting machine. In this known method the tubular article is knitted beginning at the end with the elasticated cuff and continuing to knit all the way to the edges which are joined correctly together to form the closed toe of the article. This known method is highly complex and requires a knitting machine equipped with specially formed fabric-forming members, which also raise considerably difficulties of control. Moreover the seam is produced on the outside of the article rather than on the inside as would be more desirable and as normally happens in systems in which sewing is carried out away from the knitting machine.
Methods and devices have also been suggested in which the toe of the article is closed as the initial step in a knitting process, which therefore starts with the closed end and finishes at the open end comprising the elasticated cuff. Methods and devices of this kind are described for example in WO A 95/31595, WO A 95/34702 and WO A 97/04153.
An initial object of the present invention is to provide a process or method for producing a tubular knitted article in which the tubular article is obtained with its lower end closed without requiring manual intervention to orient it.
Another object of the present invention is to provide a method of the type described above capable of closing the toe of the tubular article by a very simple sewing system and in which a seam can be produced on the inside of the article.
Another object of a preferred embodiment of the present invention is to provide a method for closing the toe of a tubular article directly on the knitting machine which knitted the article.
It is also an object of the invention to provide a very simple device, with a limited number of special fabric-forming elements, capable of closing the toe of a tubular article with no difficulties of orientation of the article.
The object of a preferred embodiment of the invention is to provide a device capable of closing the toe of the article as the final step in the knitting process, dispensing with the need to transfer the tubular article from the knitting machine to sewing machines.
These and other objects and advantages, which will become clear to those skilled in the art upon reading the test which follows, are achieved with a method for the production of a tubular knitted article with a closed toe on the circular knitting machine, in which a circular needle bed or cylinder forms the tubular article beginning at an initial edge or end and finishing at a final toe or end which is to be closed. According to the invention, the method is characterized in that at the end of the knitting of the tubular article, the latter is partly released from the needles, engaged by transfer members and then released completely from the needles and transferred to means for closing the toe.
In this way the article, being engaged by the transfer members before being completely released from the needles, arrives at means of closing the toe in a correctly oriented position without the need for manual intervention.
In one particularly advantageous embodiment of the invention, the method involves the following steps:
turning the tubular article inside out at the end of the process of knitting the courses on the needle cylinder and after having engaged it on the transfer members,
transferring the article to below the needle cylinder,
closing the second end of the tubular article, and
turning the tubular article right side out again.
The sewing or closing of the toe may take place in a machine outside of the circular machine, or inside the circular machine itself, where sewing systems, for example a small sewing machine, may be arranged.
In order to turn the article inside out in a simple and effective way, and then close the toe with a seam which, once the production process has concluded, will be situated on the inside of the tubular article rather than on the outside, an especially advantageous embodiment of the invention employs a tubular element coaxial with the needle cylinder and extending down from an upper edge located level with or slightly below the needle cylinder. During the knitting process the tubular article grows downward inside the tubular element. At the end of the knitting process, while the tubular article is still partly engages on the needles of the cylinder, the transfer members move coaxially relative to the tubular element and on the outside of this element in order to engage the article at the edges of the fabric between the upper edge of the tubular element and the needle cylinder and then pull the article down along the outside of the tubular element, turning it inside out as it passes over the upper edge of this tubular element.
At the end of the transfer process the tubular article is therefore now inside out, and still engaged on the lower portion of the tubular element, with its end that is to be closed being free underneath the lower edge of the tubular element, where a closing means, e.g. a sewing machine of a type known per se, is positioned.
Once the toe has been closed, the article must be turned inside out a second time, and thus in practice turned right side out, i.e. returned to the position in which is was originally knitted by the needle cylinder. The same transfer members can be used again for this purpose.
In a particularly advantageous embodiment, after the toe end of the article has been closed, one of the transfer members is moved until approximately coaxial with the tubular element and underneath it, and is then extended so that it enters the interior of the tubular element, taking with it the tubular article whose closed end it pushes in front of itself. The result of this is that the tubular article is turned inside out once again around the lower edge of the tubular element. From this element the article, now right side out, can be extracted by pneumatic means of a type known per se.
The device according to the invention comprises a circular needle bed, i.e. a needle cylinder, for knitting the article and is characterized by transfer members capable of engaging the tubular article at the end of the knitting process and before the article is completely released from the needles of the needle cylinder; the transfer members transfer the end of the article that is to be closed to closing means, preferably positioned underneath the needle cylinder or outside of the circular machine.
One possible and particularly advantageous embodiment of the device according to the invention employs a tubular element coaxial with the needle cylinder and extending down from an upper edge to beneath the needle cylinder. The tubular element has a smaller diameter than the needle cylinder and the transfer members are movable on the outside of the tubular element, parallel to its axis, in order to engage the tubular article close to the end which is to be closed and transfer it downward, causing it to turn inside out as it passes over the upper edge of the tubular element.
The transfer members preferably include perforating means that engage the tubular article by penetrating the knitted fabric forming the article at the fabric edges which are suitable for gripping. Because these fabric edges are cut and discarded during the closing of the article, this does not damage the final article.
The transfer members may be two in number and positioned in diametrically opposite positions with respect to the axis of the tubular element.
In a particularly simple and advantageous embodiment, the transfer members are equipped with a telescopic lengthening system, for example pneumatic or hydraulic means for extending a tubular structure. This does not preclude the use of different means, such as slides traveling along guides arranged parallel to the axis of the tubular element.
Also, advantageously, the transfer members may also be able to execute a movement perpendicular to the movement of gripping and transferring the tubular article, so that at least one of the transfer members can also be used to turn the tubular article inside out a second time (so that it ends up right side out). To this end it is advantageous if at least one of the transfer members can be moved alternately outside or inside the tubular element extending down below the needle cylinder. The second turning of the tubular article inside out (i.e. right side out) is brought about by bringing the transfer member approximately coaxially with the tubular element and then extending the transfer member axially inside the tubular element, taking with it the closed end forming the toe of the tubular article, which by this means is turned inside out as it passes over the lower edge of the tubular element. This does not however rule out the option of using separate members for the second occasion of turning the tubular article inside outxe2x80x94that is right side out; e.g. an additional slide placed in an intermediate position between the transfer members. Moreover, although this is less advantageous in terms of production and reduction of labor, it is also conceivable that the tubular article be turned right side out away from the knitting machine.
Other advantageous features and embodiments of the method and device according to the invention are listed in the appended dependent claims.